The invention relates to a ring spinning or ring twisting machine having at least one row of rotatably mounted spinning or twisting rings. More particularly, the invention relates to those machines having spinning rings that can be decelerated by means of eddy current brakes by cooperation of metallic flanges on the ring and stationary but displaceable permanent magnets which create eddy currents in the flange.
The spinning or twisting rings, henceforth only called rings, which are rotatably mounted, are normally carried on air bearings and are thus essentially friction free. The invention preferably relates to a known apparatus in which each rotatably mounted ring has associated with it a traveler that can revolve on the ring and which, because of the very high operational rpms, generally becomes stationary with respect to the ring on which it is mounted due to the centrifugal force pressing it against the ring. However, the invention is not limited to this preferred application, but it may also be used if the ring has a heel or an eye for the passage of the thread instead of having a traveler associated with it. In any case, the ring is driven in known manner by the thread which traverses the traveler or the heel or the eye in the direction of the wind-up spindle. In order to achieve a particular thread tension, it is required to be able to brake the ring with an adjustable amount of decelerating or braking torque. It is known to provide an eddy current brake of the above-described type in which the braking torque is changed by a vertical change of position of the magnets, i.e., a change of position in a direction parallel to the axis of rotation of the flange. However, such a displacement results in very large changes of the brake torque for very small changes of position of the magnet, so that, in practice, a precise setting or adjustment of the braking torque is impossible. Furthermore, this adjustment mechanism is relatively expensive and does not permit a simultaneous adjustment of all of the magnets on one machine side because of the great difficulties to achieve equal braking torques in all the different eddy current brakes.